The present invention relates to an electronic, digital display watch, and more particularly relates to a wrist-watch having solar and geographical functions. The watch includes timekeeping means for the current date and time.
Heretofore watches have been proposed which provide to time and date data. The more advanced watches count the months and years of a four-year cycle. Various watches in addition to time and date provide information relating to the sun's trajectory, for example the time of sunrise and sunset. However, such watches are restricted in that solar information is related to the time of the locality which rarely coincides with the official time which is the time at the center of the time zone being considered or at the center of an easterly time zone (summer time, double summer time). Moreover, proposed watches have provided proper solar data only for certain geographic latitude zones, or for a certain number of selected geographic latitude zones.
Also known are digital electronic wrist-watches with computing functions. Such watches amount to small pocket computers. A major drawback of such watches is the difficulty in providing a relatively large number of push-buttons needed for a pocket computer on the relatively small area of the wrist-watch. Thus several tens of required push-buttons are arrayed on the major part of the watch face. The buttons are forced to be made very small, to the extent that the buttons cannot be finger actuated but demand the use of a sharp point similar to the tip of a ball-point pen. Still these computer-watches only amount to a pocket computer of low sophistication, permitting the four basic operations and several similar functions. Such watches do not allow complex programming with different sequential operations, requiring storage of a complex program.
Presently there is an increased interest by persons in ability to gather solar position information under different circumstances. Such persons include the increasing number of persons engaged in installing solar energy receiving means; architects and urban planners dealing with shade and shade direction; and pilots and airplane passengers involved in long distance flights wishing to know when night, day, sunset etc., shall take place. Another category of persons wishing to know solar position parameters, are the faithful of the Moslem religion for whom prayer hours are determined by the path of the sun. For example, the time of interrupting the Ramadan fast--which is defined as the time of complete night fall--can be physically defined as the time when the sun has dropped about 12.degree. below the horizon. The moment this takes place varies with latitude and the period of the solar year. The Ramadan shifts progressively from summer to winter and vice versa in a cycle of about 30 years.
In view of the above, it is clear that particularly interesting computing functions for integration into a watch are those relating to the sun. On the other hand, existing computer watches are designed for general use, not particularly for solar computation operations nor can they store the very complex programs.
The prior state of the art therefore suffers from gaps regarding a computing watch of the particular type discussed above, and which, in spite of its specialized functions, should permit operation by means of a small number of push buttons which are easily actuated with fingers without cluttering the watch face, and under these conditions making possible permanent or semi-permanent storage of complex computing programs, again in view of the above cited specialization. Note should be taken also that as regards existing computer watches, most of the watch face is taken up by push-buttons so that the display area is small, whereby only a few digits can be displayed or else the display characters must be quite tiny. This drawback should be eliminated in the above considered special watch.